From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 7CF423853804; Fri,  8 Apr 2022 12:18:44 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7CF423853804
From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/105198] [9/10/11/12 Regression] Wrong code
 for C loop (GCC 12 -O2, GCC 11 -O3)
Date: Fri, 08 Apr 2022 12:18:44 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: cvs-commit at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 9.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-105198-4-J1lohH5BB7@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-105198-4@http.gcc.gnu.org/bugzilla/>
References: <bug-105198-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Fri, 08 Apr 2022 12:18:44 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105198

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:e5453bcc217ea4ac53a4ac277661d6ef0ccd425b

commit r12-8059-ge5453bcc217ea4ac53a4ac277661d6ef0ccd425b
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Apr 8 13:13:29 2022 +0200

    tree-optimization/105198 - wrong code with predictive commoning

    When predictive commoning looks for a looparound PHI it tries
    to match the entry value definition (a load) up with the appropriate
    member of the chain.  But it fails to consider stmts clobbering
    the very same memory location inbetween the load and loop entry.

    In theory we could be more clever on must aliases that would be
    also picked up from a load (so not exactly stmt_kills_ref_p) and
    use the stored value from that if it is an exact match.  But we
    currently have no way to propagate this information inside predcom.

    2022-04-08  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/105198
            * tree-predcom.cc (find_looparound_phi): Check whether
            the found memory location of the entry value is clobbered
            inbetween the value we want to use and loop entry.

            * gcc.dg/torture/pr105198.c: New testcase.=